diff [options] from-file(修改前的文件) to-file(修改后的文件)
diff 的 options
-u # Use the unified output format. -r # When compare directories, recursively compare any subdirectories found. -d # Change the algorithm to perhaps find a smaller set of changes. This makes diff slower (sometimes much slower). -q # Report only whether the files differ, not the details of the differences.